Conversion system for use in electronic calculators

ABSTRACT

A conversion system for an electronic calculator employs a shift register and a full adder circuit to convert binary digit signals for decimal display purposes. The shift register and full adder include appropriate gating and delay-feedback circuitry for serial conversion, column shift, and read-out.

United States Patent- Hatano et al. 1 Dec. 5, 1972 [54] CONVERSION SYSTEM FOR USE IN [56] References Cited ELECTRONIC CALCULATORS UNITED STATES PATENTS [72] Inventors: lsao Hatano; Akira Nagano; Kenzi Yosimoto a of Kyoto, Japan 2,886,241 S 5/1959 Spauldmg et al. ..235/154 2,860,327 11/1958 Campbell ..235/l55 Asslgnee: 0mr0n Tatelsl Electronics -y 3,214,576 l0/l965 Propster, Jr. ..235/170 x Kyoto-shi, Japan Primary Examiner-Maynard R. Wilbur [22] Flled' 1970 Assistant Examiner-Leo H. Boudreau [2]] App]. No.: 99,090 Attorney-Craig & Antonelli [30] Foreign Application Priority Data [57] ABSTRACT A conversion system for an electronic calculator em- 19-69 3 ploys a shift register and a full adder circuit to convert binary digit signals for decimal display purposes. The l 2% 'i 3 235/155 235/17g shift register and full adder include appropriate gating 1 I.- delay feedback circuitry f i lconversion, [58] Field of Search ..235/154, 155, 170, 169; column Shift and feadflut;

- 340/347 DD v 9 Claims, 7 Drawing Figures 4 5 2 HALF 5 UEVIEE AUUER l FULLADUER- l 10 72 73 FLIP-FLOP 2 1 o V HALF SHIFT. 2 J, AUDER REGISTER %4 21 RELATED T0 c1 23 SSHIFATL' 75%L [3N "tlz" "t2'1'BlNARYCUDE0U10 20 B'NARYEUUEUW "IB BINARYEUUE'UlUU' 77 9 FLIP-FLOP P'A'TE NTTEDBEE 51912 SHEET 10F 3 DISPLAY 7 DEVICE 2 FULL g i MR4- SHIFT SHIFT I F REGISTER T REGISTER T 3 1. .J /6 I I E SHIFT I REGISTER. T g 1 r' I 1 IBIT DELAY c mcun 1 I 1 7 L I l L J 'CT'EULUMN SHIFT SIGNAL F/G.2; SHIFT DISPLAY 5 2 HALF '6 REGISTER DEVICE ADDER FULL 1110511; I FLIP-FLOP H 72 l HALF sum 3 Z 1 0 T? H, TADDER REGISTER 8 9 14 21 ELATED m m 23 511111 76 J SIGNAL r I "tZ'BINARYEUUE'UUlU 20 B'NARYEUDE [mm "131' mARvcunE'muo' 19 76 FLIP-FLOP v INVENTORS \SRO mam, mum memo a KENZ! voswm 1 CONVERSION SYSTEM FOR USE IN ELECTRONIC CALCULATORS The present invention relates to electronic calculating machines and, more particularly, to a conversion system of a nature generally applicable to such calculating machines and by which a certain combination of four binary digitsrepres enting adecirhal number having a plurality of columns, that is, a decimal number of not less than (l), can be converted intoa correspond-- ing number of combinations of four binary digits, each of these combinations representing a decimal number of less than l0). I

It is well known that, when the decimal number is to be added. tothedecimal number (6) with the use of an electroniccalculator, a binary code 0101 representative of the number (5) is added to a binary code 01 representative of the number (6) in the arithmetic cir- However, the electronic calculators generally available are provided with a digital display device including a p lurality of read-out means, for example, read-out tubes each capable of selectively illuminating oneof the decimal numbers. zero through nine, so that a predeterminedcombination of decimal digits can be illuminatedto correspond with a given binary code. If the'binary code 10] l is merely impressed on the digital display device, the corresponding decimal digits (II) will not be displayed. In order to display the decimal digits (ll) whichrepresent the sum of (5- 6), it is necessary to convert the binarycode 101 1 into a pair of binary combinations 000l ,and 0001, to cause each of the read-out tubes to illuminate the digit (1 Accordingly, the object of the present invention is to provide a converting system capable of performing this operation. The invention is more specifically defined in the appended'claims.

Other objects and features of the invention will become apparent from the-following description taken by way of-example with reference to the accompanying drawings, in which,

FIG. I is a schematic block diagram: of the circuitry employed in an electronic calculator;

FIG. 2 is a portion of the circuitry of FIG. 1 showing a converting circuit according toa preferred form of the present invention; 1

FIG. 3 is a schematic diagram of various pulses employed in the present circuits showing their timing with respect to one another;

FIG. 4 shows an arrangement of bits in a shift register in the preferred embodiment of the present invention, wherein FIG. 4(a) is a schematic diagram showing each stage composed of four hits and FIG. 4(b) is a schematic diagram showing a manner in which each bit is shifted to the right; and

FIG. 5 shows a stage arrangement of the shift register of the preferred embodimenhwherein FIG. 5(a) is a schematic diagram showing the shift register composed of {5 stages and FIG. 5(b) is a schematic diagram showing a manner in whicheach decimal digit is shifted from one stage to another.

Referring now to FIG. I, the serial arithmetic circuitry generally includes three shift registers 1, 2 and 3, a full adder 4 and a display device 5.'E ach of these shift registers 1, 2 and 3 and the full adder 4 is of the serial means are omitted from the drawings for the purpose of simplification of the description.

The arithmetic circuit so constructed can be operated by such 'pulse trains as clock pulses t1, t2, t3 and t4, shift pulses T1, T2 T7 and T8 and transfer pulses 7A and TB, particularly as shown in FIG. 3. In the example shown, one decimal digit B can be expressed by various combinations of binary digits a 01. 01 and a1 wherein numerals of the suffix 8, 4, 2 and l represent the 2 2 2 and 2 positionslf the number of stages of the shift register is assumed to be eight, 32

. bits are provided-for, the number having eight decimal digits ,8 B, 3 and fi insequence, wherein numerals 8 to I represent the l0, l0 l l0 and'l0" columns, respectively. In this example, four clock pulses t1, t2, t3 and t4 are employed to shift each bit of the register to the right. For shifting one decimal'vdigit B from one stage to another, shift pulses TI to T8 are employed. The whole contents of any oneof the shift registers can be transferred during the duration of a single transfer pulse rA or 1B.

The four binary digits 0a,, a a and a, representative of each decimal digit a that has been stored in the re described,the sum of numbers each expressed by a combination of four bits circulated in the register 2 should be less than 10). By way of example, in the case where the decimal number (6) is stored in the register 2 while the decimal number (5) is stored in the register 3, a trainof pulses representative of the binary. digits 10ll, representative of the decimal sum of the above two numbers, will be generated by the adder 4. However, even when the train of pulses thus generated is merely applied to the display device 5 through the register 2, the read-out tube does not show the figure (11).

In order to cause the display device 5 to show the figure (I l which is the sum of (5 6), the binary combinations 0000, 101 l circulated in the register 2 should be converted to give a pair of binary combinations- 0001, 0001 whereby the left-hand binary combination represents the most significant digit of the decimal number (1 I) while the right-hand combination represents the least significant digit thereof. A system for performing such conversion is particularly shown in FIG. 2.

Referring now to FIG. 2, the system shown is a detailed circuit of the register 2 of FIG. 1 and includes flip-flops 8, 9, l0 and 11, the combination of these flipflops corresponding to one binary digit. These flip-flops 8 to 11 are connected in series with each other and in series with a half adder 12. The maximum number of decimal digits that can be stored by the register 2 is substantially equal to the sum of the number of decimal digits to be stored by the flip-flops 8 to 11 and the maximum number of decimal digitsto be stored by the register 13. These flip-flops 8 to 11 are adapted to store the most significant digit of the decimal number to be stored by the register 2.

Respective outputs of the flip-flops 9 and are applied to one input terminal of a first AND gate through a first OR gate 14, while the output of the flipflop 8 is applied to the other input terminal of the gate 15. The output of the gate 15 is impressed on one input terminal of a second AND gate 17 through a second OR gate 16, while the other input terminal of the gate 17 receives a signal t1 generated by a clock pulse generator (not shown).

As shown in FIG. 3, this signal :1 is the first one of the clock pulses tl,'t2, t3 and t4 which are respectively adapted to shift binary digits in the 2, 2', 2 and 2 positions. lnother words, while the contents stored 'in the arithmetic circuit are circulated by these clock pulses t1 to t4, each decimal digit is shifted to the right and finally read-out by the display device.

The output of the second AND gate 17 can'be stored in a flip-flop 18, the output of which is received by a third AND gate 19. This AND gate 19 also receives the output of a third OR gate 20 to which the signals t2 and t3 are individually applied. Accordingly, since the third 7 In this arrangement, when a certain decimal number composed, for example, of two digits, is to be applied to the input of the flip-flop 8, a pulse train representative of binary digits 01 a}, 0: and a, which correspond to the most significant digit of the decimal number can be respectively applied'to the flip-flops 8 to 11 by the clock pulses 1 to t4, in the sequence a 01 01 and 01 during one cycle of operation, and another pulse train representative of binary digits a a a and a, which correspond to the next most significant digit, that is, the least significant digit in this example, can be respectively applied to the flip-flops 8 to 11 by the clock pulses 1 to 4, in the sequence 01,, a a, and a during the following cycle of operation, while the binary digits a a}, 1x and (1 have been transferred to the register 13 through the half adder 12, as shown in FIG. 4.

FIG. 4(a) shows the form taken by each of the shift registers, these being divided into eight stages, identified as the 10, 10, 10 down to 10 stage. Each stage contains four binary digit positions 2 2 2 and 2. The gate shown symbolizes the recirculation procedure.

- FlG. 4(1)) demonstrates how each bit is shifted to the right and recirculated by successive clock pulses :1 to t4 of successive shift pulses T1, T2 etc. For example, the bit a," in position 2 of stage 10 at the first time t1 is moved by the next pulse :2 to the next position to the right, i.e. into position 2 v of stage 10. Similarly all the other bits are simultaneously moved to the right, the bit in position 2 of stage 10 (i.e. bit a, at pulse :4, T1)

being recirculated to position 2 of stage 10 at the next pulse,'i.e. t1, T2, and so on.

FIG. 5(a) shows the stage arrangement only of each shift register, again with the gate symbolizing the recirculation. FIG. 5(b) shows the progress of the information around the register for each shift pulse T1 to T12 of a typical transfer pulse period '1', the information here being represented by the decimal digits [3,, to [3,.

However, in this example, the binary digits corresponding to one decimal digit have been stored in the flip-flops 8 to 11 prior to the generation of the clock pulse t1. Accordingly, if the binary digit a in the 2 position is 1 and/or the binary digit a, in the 2 position is l, the first OR gate 14 will be turned on to generate a signal representative of l to the first AND gate 15. This AND gate 15 will in turn generate a signal representative of 1 only when the binary digit 0: in the 2 position is 1. Accordingly, the output of the AND gate 17, when the clock pulse t1 is applied thereto, will be 1. In other words, when the binary digits stored in the flip-flops 8 to 11 is 1010 or more than l0l0, i.e., not less than the decimal number (10), the second AND gate 17 generates an output representative of l By way of example, assume now that the binary digits llOl corresponding to the decimal number (13) are stored in the flip-flops 8 to 11. Respective outputs of the flip-flops 10 and 9 are 0 and 1 so that the OR gate 14 feeds a signal representative of l to the first AND gate 15. Since the output of the flip-flop 8 is also I, this AND gate 15 feeds a signal representative of l to the second AND gate 17. When this signal 1 is thus applied to the gate 17 and the clock pulse t1 is simultaneously applied thereto, the gate 17 generates a signal representative of l, to bring the flip-flop 18 into the set position, so that the signal l is applied through the flipflop 18 to the corresponding input terminal of the third AND gate 19. Since the other input terminal of this gate 19 receives the output of the third OR gate 20 to which the clock pulses t2 and t3 are respectively applied, the output of the gate 19 will be a pulse train representative of:

This pulse train is impressed on the full adder 22 as the following four hits (b) of the flip-flops 8 to 11 are sequentially applied to the full adder 22:

l l0l (b) These binary digits (a) and (b) are added by the full adder 22 to give the following sum:

* The leftmost digit as marked with an asterisk, that is,

(l), of the binary sum (c) is used as a column shift signal C2, while the remaining digits 0011 are transferred to the register 13. Since the column shift signal C2 is provided, the following binary combination for the 10 position will be formed into 000'] by the column shift signal C2. From the foregoing description, it will be understood that the binary combination representing the decimal number (13) within a four-binary frame is converted into 001 l representative of the least significant digit (3) while the following binary'combination is formed into 0001 representative of the most 

1. A conversion system for use in an electronic calculator comprising: a first shift register having a predetermined number of stages for receiving a series of binary digital signals representative of a number to be entered in said calculator; first means, responsive to the states of the stages of said shift register, for detecting the storage of digital signals therein corresponding to a decimal number of at least a predetermined value; second means, coupled to said first means, for generating binary signals corresponding to a prescribed decimal number; third means, responsive to the contents of said shift register and said second means, for serially adding the outputs of said shift register to the binary signals generated by said second means; said third means including an adder circuit and a delay means, coupled between the output and an input of said adder circuit, for delaying a column shift signal generated by said adder and applying said column shift signal to said adder circuit; fourth means, coupled to said delay means and to said shift register, for generating a signal when said column shift signal is supplied to said fourth means upon a specified condition of the stages of said shift register; and fifth means, responsive to said first and fourth means, for enabling the delivery of the binary signals generated by said second means to said adder circuit, together with the contents of said shift register to be added in said adder circuit.
 2. A conversion system according to claim 1, wherein said first means comprises a first OR gate means connected to the outputs of predetermined stages of said shift register and a first AND gate means connected to said first OR gate means and to a stage of said shift register.
 3. A conversion system according to claim 2, wherein said fourth means comprises a second AND gate means connected to said shift register and to the output of said delay means.
 4. A conversion system according to claim 3, wherein said fifth means comprises a flip-flop circuit coupled to the respective outputs of said first and second AND gate means and a third AND gate means connected to the output of said flip-flop and said second means, and wherein the output of said third AND gate means is connected to said adder circuit.
 5. A conversion system according to claim 1, wherein said fifth means comprises a flip-flop circuit coupled to the respective outputs of said first and second AND gate means and a third AND gate means connected to the output of said flip-flop and said second means, and wherein the output of said third AND gate means is connected to said adder circuit.
 6. A conversion system according to claim 4, wherein said second means comprises a second OR gate means receiving binary timing signals, corresponding to said prescribed decimal number, for supplying said timing signals to said third AND gate means.
 7. A conversion system according to claim 6, further inCluding a third OR gate means connected between the outputs of said first and second AND gate means and a fourth AND gate means connected to the input of said flip-flop.
 8. A conversion system according to claim 7, further including means for supplying respective binary timing signals for controlling the operation of said system.
 9. A conversion system according to claim 8, wherein said adder circuit comprises a half-adder. 